Procedure and device for specific particle manipulation and deposition

ABSTRACT

A process for manipulating particles distributed substantially non-uniformly in a plasma of a carrier or reaction gas, wherein Coulomb interaction between the particles is so low that the particles substantially do not form a plasmacrystalline state, and the particles are exposed in a location-selective manner to external adjustment forces and/or the plasma conditions are subjected to a location-selective change to apply at least a portion of the particles onto a substrate surface mask-free and/or subject it to a location-selective plasma treatment in the carrier or reaction gas.

RELATED APPLICATION

This is a continuation of PCT/EP99/02241, with an international filingdate of Apr. 4, 1999, which is based on German Patent Application No.198 14 871.2, filed Apr. 2, 1998.

FIELD OF THE INVENTION

This invention relates to a procedure and device for the specificmanipulation and/or deposition of microscopic particles inhigh-frequency plasma.

BACKGROUND

As is generally known, formation of high-frequency plasma in therespective reaction gas is a suitable means for achieving the desireddegradation reactions or the like for processing or degradationprocedures such as plasma etching, or chemical vapor deposition (CVD).To optimize CVD applications, e.g., for separating amorphous,hydrogenated silicon (a-Si:H) for photovoltaic devices, thin-filmtransistors, flat-screen displays or color detectors in imaging systems,there are numerous studies on how the properties of deposited layersdepend on plasma parameters, e.g., the types of reaction gas, HF voltageor gas pressure. It has been shown that microscopic particles (so-called“particles”) can form in the plasma and have a disruptive orfacilitative effect on the layer properties, depending on theapplication.

For example, in “Appl. Phys. Lett.”, Vol. 69, 1996, pp. 1705 forward, D.M. Tanenbaum et al. describe the formation of particles in plasma duringa-Si:H deposition as follows: Negative ions are formed in the silanereaction gas as the result of electron bombardment, and react in theplasma with radicals and cations. This produces growing particles, whichhave a negative charge, as the electron velocities are significantlyhigher in comparison to the cation velocities. Due to the formation ofspace charge regions near the electrodes, these particles, which cangrow to μm dimension sizes, to not get to the substrate, which generallyis secured to one of the electrodes. D. M. Tanenbaum et al. showed that,despite the space charge zone, particles ranging from roughly 2 to 14 nmin size reach the substrate during plasma discharge and, once there, cantrigger disruptions in the layer properties.

In the “14^(th) European Photovoltaic Solar Energy Conference”(Barcelona 1997), Paper No. P5A.20, P. Roca i Cabarrocas et al. describea significant improvement in charge carrier transport in a-Si:H layersby embedding particles. The particles arise under specific pressureconditions in the reaction gas, and are identified by characteristic,so-called “hydrogen evolution” measurements in the layer. The layerscontaining the particles exhibit a considerable increase in darkconductance and photoconductivity in comparison to amorphous layers. Inaddition, a considerable improvement was achieved in the stability ofphotoelectric properties under illumination.

One general problem in the previous studies on the effects of particlesin CVD deposited layers is that a means for the targeted andreproducible handling of particles occurring irregularly in the reactiongas has thus far not been available. A particular problem in this caseis that the particles can arise within roughly 1 second at the usualplasma frequencies of about 14 MHz.

Additional aspects of particle formation are illustrated below makingreference to a conventional device according to FIG. 13.

In a plasma state, e.g., generated by a glow or gas discharge, a gasencompasses particles of varying charge, e.g., positively or negativelycharged ions, electrons and radicals, but also neutral atoms. Ifmicroscopic particles (up to several 10 μm in size), e.g., dustparticles, form or exist in the plasma, these take on an electricalcharge. The charge can reach several hundred thousand electron chargesdepending on the particle size and plasma conditions (type of gas,plasma density, temperature, pressure, etc.).

In the known device shown in FIG. 13, two flat discharge electrodes 11and 12 are arranged one atop the other in a reactor (vessel walls notshown) with a carrier gas. The lower circular or disk-shaped HFelectrode 11 is actuated with an alternating voltage, while the upper,annular counter-electrode 12 is grounded, for example. The electrodedistance measures roughly 2 cm. A control circuit 13 is set up toconnect the HF generator 14 with the HF electrode 11 and actuate thegrounding and separation circuit 15 of the counter-electrode 12. Thehigh-frequency energy can be injected with a frequency of 13.56 MHz anda power of roughly 5 W, for example. The carrier gas is formed by inertgases or reactive gases at a pressure of approx. 0.01-2 mbar.

A state of equilibrium preferably sets in among the particles, in whichthe gravitational force G acting on the particles is balanced with anelectrical field strength E, to which the particles are exposed as theresult of a space charge near the HF electrode 11 as a function of theircharge. Also known is the formation of plasma crystalline states ofparticle configurations, but this is limited to particles withcharacteristic dimensions exceeding 20 nm, since the respectivelycarried charge is so low for smaller particles that thermal fluctuationshave a stronger influence on the particles than the Coulomb interactionsrequired for the plasma crystals, so that a uniform structure cannot beformed. In addition, formation of plasma crystals was previously limitedto particles introduced into the reaction space from outside, e.g. dustparticles. Therefore, a targeted handling of nanocrystalline particles,in particular with characteristic sizes of a few to several 10 nm, couldnot be derived from the manipulation of particles arranged in aplasmacrystalline manner.

However, in view of the known influence of structural or photoelectricproperties of deposited layers resulting from built-in nanocrystallineparticles, there is a strong interest in being able to control particleincorporation, in particular with regard to the type, size, number andposition of the particles.

The manipulation of particles in a plasmacrystalline state is known fromPCT patent application WO 98/44766 being published after the prioritydate of the present patent application. In JP 04-103769, aLaser-CVD-procedure is described.

Thus, it would be advantageous to provide a method for the specificmanipulation or separation (deposition) of particles in or from plasmas,in particular, for influencing the particles themselves or modifying asubstrate surface or a layer, and a device for implementing theprocedure.

SUMMARY OF THE INVENTION

When exposed to a sufficiently energetic irradiation, which triggers inparticular a discharging or reversing the charge of the particles, orexerts a light pressure, particles that arise internally in the reactionspace with an ignited plasma, or are provided to the reaction space fromoutside (externally) and initially have a negative charge, are moved toan altered target position from an initial position corresponding to theforce equilibrium of the negatively charged particles. The particles canhave sizes ranging from several nanometers to roughly 100 μm. Theenergetic irradiation can encompass laser radiation to trigger adischarge, a UV laser or electron irradiation for reversing particlecharge via secondary electron emission, or light irradiation to generatea light pressure. The target position of the particles can be a rangewith altered plasma conditions, or a substrate on which the particlesare applied alone or simultaneously with layer formation via plasmadeposition.

The nanoparticles exhibit a substantially non-uniform spatialdistribution in the plasma. This means that the nanoparticles arerandomly distributed relative to each other, at statisticallydistributed locations. To this end, the conditions in the reactionspace, in particular the plasma conditions, e.g., the ratio of electronsto ions in the plasma, are adjusted depending on the particles in such away that the particles possess such a high energy that substantially noordered or plasma crystalline states are formed.

A special advantage to the invention is that the energy-rich irradiationof the particles initially distributed substantially non-uniformly inthe plasma takes place in a location-selective manner, so that particlesare exposed in the form of a masking of altered plasma conditions inpredetermined, selected plasma areas, or applied to the substrate basedon a deposition pattern.

The equilibrium in particular between the gravitational force andelectrical forces on the particles in the initial position can also beinfluenced by a location-dependent change in a static or low-frequencyalterable electrical field between the electrodes of a plasma reactor(exertion of external adjustment forces). In this way, the particles inthe plasma can be arranged on surfaces curved in whatever way with anyedges. Therefore, the particles in the plasma can be moved in apredetermined manner, wherein this movement is even reversible, so thatthe particle arrangement can be adjusted between various conformations.

Another aspect of the invention is that the location-selectivedeformation of a substantially non-uniform particle arrangement subjectsit to different plasma conditions in various partial subdomains. Thisenables a location-selective plasma treatment of particle areas (e.g.,coating or stripping), in particular in plasma between two essentiallyflat electrodes. Application to a substrate can follow such alocation-selective particle treatment.

In addition, an aspect to the invention lies in the fact that theformation of a particle arrangement is not influenced by the presence ofa substrate in a plasma reactor, in particular, between reactorelectrodes for generating a glow or gas discharge. In particular, it ispossible to perform the aforementioned conversion processes in directproximity to a tabular, flat or bent substrate, and then to reduce thedistance between the particles in the particle arrangement and substratesurface in such a way that at least a predetermined portion of theparticles is applied to the substrate surface. The reduction in distancecan either be achieved by influencing the field strengths that hold theparticles in position, or by moving the substrate surface. As a result,the particles can be deposited on substrate surfaces in patternsconfigured as desired. Therefore, the invention provides a novel,location-selective, mask-free coating procedure with which modifiedsurfaces are generated. The applied particles give the modified surfacesaltered electronic, optical and/or mechanical properties. However, it isalso possible to use the particles applied in a location-selectivemanner themselves to mask or condition the substrate surface before orduring an ensuing additional coating step.

A device according to the invention for manipulating particlesencompasses a reaction vessel, which contains means for generating aplasma and at least one substrate. The means for generating the plasmapreferably consist of tabular, essentially parallel electrodes, betweenwhich the substrate can be moved. The electrodes in the reaction vesselcan exhibit field-forming structures for the location-selectiveinfluencing of the particles. The reaction vessel can also contain meansfor location-selective particle discharging (e.g., UV lighting meanswith a masking device), means for exposing the particles to radiationpressure, monitoring means and control means.

One special aspect of the invention involves configuring the electrodesfor the location-selective influencing of particles in the reactionvessel. According to the invention, an electrode arrangement (oradaptive electrode) is described that exhibits numerous electrodesegments, which are actuated substantially simultaneously with ahigh-frequency voltage, and each individually with a segment-specificdirect voltage or low-frequency voltage. The high-frequency voltagegenerates or maintains a plasma state in the reaction vessel, while thedirect or low-frequency voltage generates a static or slowly variablefield distribution (field E) in the reaction vessel, during exposure towhich the particles become arranged or move in the reaction vessel.

Additional features of the adaptive electrode include the formation of amatrix arrangement comprised of miniaturized electrode segments, theshaping of the matrix arrangement as an essentially flat, laminatedcomponent, whose electrode side faces the reaction vessel, and whosebackside carries control electronics, the pressure relief of thecomponent, e.g., via the generation of a vacuum in the space which theback of the electrode arrangement faces, and the provision of atemperature control device for the control electronics.

BRIEF DESCRIPTION OF THE DRAWINGS

Details and advantages to the invention will be described below makingreference to the attached drawings. Shown on:

FIG. 1 is a diagrammatic side view of a device according to theinvention for manipulating particles;

FIG. 2 is a diagrammatic top view of a part of the device according toFIG. 1;

FIG. 3 is a diagrammatic illustration of an electrode configurationaccording to the invention for manipulating particles, and examples of alocation-selective substrate coating;

FIG. 4 is an exploded view of a reaction vessel provided with anadaptive electrode according to the invention;

FIG. 5 is a diagrammatic top view of an adaptive electrode according toFIG. 4;

FIG. 6 is a diagrammatic perspective view of a sub-unit of the adaptiveelectrode shown on FIGS. 4 and 5, with the accompanying switchingelectronics;

FIG. 7 is a block diagram to illustrate the control of an adaptiveelectrode according to the invention;

FIG. 8 is a diagrammatic illustration of another example forlocation-selective substrate coating;

FIG. 9 is a view to illustrate another example for a location-selectivesubstrate coating;

FIG. 10 is a diagrammatic top view of a modified device for manipulatingparticles and another example for a location-selective substratecoating;

FIG. 11 is a diagrammatic illustration of a substrate coating withso-called “Bucky Tubes”;

FIG. 12 is a diagrammatic top view of another embodiment of a deviceaccording to the invention for manipulating particles; and

FIG. 13 is a diagrammatic perspective view of a conventional reactor(prior art).

DETAILED DESCRIPTION OF THE INVENTION

In the following, the invention will be described based on the exampleof a plasma device, wherein the device is a reaction vessel thatencompasses a reactor whose structure essentially reflects theconventional design as described above in reference to FIG. 13 in termsof plasma generation and particle observation. However, as the skilledperson knows, reactors can also be configured differently, provided theyare set up to manipulate particles according to the invention in aparticle arrangement.

The following description relates to two specific embodiments, whereinthe first embodiment relates to the manipulation or deposition ofparticles introduced into the reaction vessel from outside, and thesecond embodiment relates to the manipulation or deposition of particlesgenerated inside the reaction vessel. However, it will be appreciatedthat the following description is intended to refer to specificembodiments of the invention illustrated in the drawings and is notintended to define or limit the invention, other than in the appendedclaims. Also, the drawings are not to scale and various dimensions andproportions are contemplated.

First Embodiment

The following explanation relates to the manipulation of particles thatare represented as an essentially planar particle arrangement for thesake of clarity, and labeled with the reference numerals 10, 20, 40, 50,60 and 70. These particle arrangements are generally non-uniform, andcan encompass mono- or multi-layers. The nanoparticles preferably rangein size from a few nanometers to about 10 nm, but can also be larger,and are formed inside the reactor or supplied from outside.

The diagrammatic side view of a device for manipulating particlesaccording to FIG. 1 shows a HF electrode 11, a groundedcounter-electrode 12, a control device 13, an HF generator 14 and aswitching device 15. A monitoring lighting source 16 with a cylindricallens arrangement 16 a, monitoring means in the form of a CCD camera 17with magnification optics 18 and an accompanying control device 19constitute optical monitoring means which need not absolutely beprovided (in particular in the second embodiment, as described below).Very small (<100 nm) particles require a different monitoring means(e.g., involving the use of Bragg scattering). A dust dispenser 21 witha reservoir 22, a conditioning device 23 and an inlet means 24 is set upto bring particles into the space between the HF electrode 11 andcounter-electrode 12. The conditioning device 23 can contain aprecharging device for the particles, for example.

The device according to the invention also encompasses a substrate 30that can be moved in all spatial directions with an adjustment device31. FIG. 1 does not show the wall of the reaction vessel, which forms anenclosed space for the carrier gas and incorporates the electrodes 11,12, the substrate 30 and parts of the particle inlet device in a vacuumtight manner. The wall can additionally exhibit windows for incouplingand outcoupling radiation.

FIG. 2 shows a diagrammatic top view of parts of the device according tothe invention shown in FIG. 1, namely the HF electrode 11 and thesubstrate 30 with the adjustment device 31. Also depicted is adischarging device 24 not shown in FIG. 1, which is set up for thelocation-selective discharging of particles. In the example shown, thedischarging device 24 encompasses a UV radiation source 25 and asuitable imaging and masking system 26, e.g., with which a group ofparticles or particles in predetermined spatial areas can be irradiatedin a location-selective manner and be discharged under exposure to UVradiation.

The UV radiation source 25 and the imaging and masking system 26 canalternatively also constitute a charge-reversing machine 24. In thiscase, the power of the UV radiation source 25 is selected in such a waythat secondary electron emissions arise on the particles during UVillumination, which result in the net charge of the particle beingpositive. Instead of the depicted embodiment of an expanded UV radiationsource 25, a narrowly limited, intensive light source can also beprovided, e.g., in the form of a UV laser, wherein the imaging andmasking system 26 is then set up for incremental, sequentialillumination of the area of the particle arrangement 10 in question. Inthis case, UV irradiation preferably takes place from above through theannular electrode 12.

As an alternative, the component 25 can also denote an electron sourcefor discharging, wherein the component 26 then represents a beam guidingsystem. The beam guiding system is used to direct the electron beam fromthe electron source to the areas of the particle arrangement ofinterest, in order to reverse the charge of the particles located therevia secondary electron emission. This injection of the electron beamalso preferably takes place from above through the annular electrode 12.

In the following, a first variant of the procedure according to theinvention for manipulating the particles in plasma will be explained,drawing reference to FIGS. 1 and 2.

Plasma is ignited in a carrier gas in the reaction vessel (not shown),in particular between the HF 11 and counter-electrodes 12, which act asthe discharge electrodes. One particular advantage to the firstembodiment is that no special requirements need be placed on the type ofcarrier gas. The plasma conditions (type and density of gas, HF power,frequency, pressure, etc.) can be selected by the skilled person basedon the conditions of the particle arrangement. For example, low-energyargon discharges or silane discharges can be used under the conditionsemployed for plasma deposition in semiconductor engineering. The use ofa reactive gas, e.g., silane, is advantageous for subsequent treatmentsteps on the particles. The energy of the ions in the plasma essentiallycorresponds to the gas temperature. The latter is determined by thedischarge conditions and, if necessary, by an outside cooling device.Therefore, for example, a nitrogen cooling system (not shown) can beprovided in a device according to the invention.

The particles to be manipulated can be introduced into the electrodespace via the dust dispenser 21. The particle size ranges from severalnm to about 100 μm. The lower limit for particle size is determined bythe pressure conditions in the reaction vessel, and via the charging.The particles should be heavy enough that the particles execute avertical motion in the plasma-free state under exposure to thegravitational force and do not remain suspended. The upper limit forparticle size is determined by the so-called “Debye length” of theinteraction between adjacent particles. The Debye length rises inproportion to the root of the plasma temperature, or inverselyproportional to the root of plasma density. Another special advantage ofthe invention is that, other than the size requirements on the particlesto be manipulated, there are no other limitations relative to the shapeor material of the particles. Any, e.g., round, needle-shaped, tubularor laminar particles, can be used. The particles must be solid orexhibit sufficient dimensional stability under the plasma conditions.Use is preferably made of a material that possesses special electricalor optical properties in the particle size range in question. A materialconsisting of various substances, e.g., organic materials, can also beused.

The particles incorporated into the plasma form a particle arrangement10 (see FIGS. 1, 2). This can be any random particle arrangement.

The HF electrode 11 exhibits a negative d.c. voltage. At an electrodediameter of roughly 8 to 10 cm, an electrode spacing of roughly 2 cm anda preliminary voltage at the HF electrode 11 of roughly −15 V, polymerparticles with a characteristic size of roughly 7 μm become arranged inthe form of a planar-shaped cloud at a distance of roughly 0.5 cm fromthe HF electrode 11.

The system dimensions specified here as an example changecorrespondingly given altered electrode parameters (electrode diameter,electrode spacing, voltage levels). The electrode diameter, for example,can lie between a few centimeters and 60 cm, while the electrode spacingcan range from about 1 cm to about 10 cm. Preferably those electrodeparameters that are compatible with available and CVD reactors areselected.

The substrate 30 is arranged between the HF electrode 11 and particlearrangement 10. There are advantageously no limitations with regard tothe substrate material and substrate shape as well. In particular, botha conductive or non-conductive substrate can be used without alteringthe conditions for the particle arrangement.

In a procedure according to the invention for manipulating particles,the particles are first situated in an initial or treatment position.This treatment position can correspond to an equilibrium of forces afterintroducing the particles into the reactor. However, it is also possibleto move the particle arrangement 10, in particular, to alter therelative position vis-à-vis the electrodes or the substrate. Forexample, this is done by altering the plasma or field conditions. Thismakes it possible to alter the carrier gas density to achieve a changein the particle charge and, hence, a change in the state of equilibriumbetween the force of gravitation and electrical power. The same holdstrue when altering the negative preliminary voltage of the HF electrodeor given an outside discharging of the particles. In the treatmentposition, at least one portion of the particles is subjected to a plasmatreatment or applied to the substrate in a subsequent step.

Plasma treatment can encompass a particle surface coating or ablation,for example. In the latter case, for example, the particle arrangementcan be incrementally lowered to a small distance from the HF electrode,as a result of which the lowermost layers of the particle arrangementbecome exposed to a selective plasma etching process. A plasma changeduring continuous reactor operation can be provided for particlecoating, if needed.

Any suitable change in the distance between the particle arrangementsand substrate surface can be used for application on the substrate 30.In a first alternative, the particle arrangements are lowered onto thesubstrate by changing the plasma conditions or through a targeted,location-selective discharge. In a second alternative, the substrate canbe lifted to the particle arrangement with the adjustment device 31. Ina third, preferred alternative, the discharge between the electrodes isdeactivated, so that the plasma is extinguished, and the particles fallon the substrate. When the particles and substrate come into contact,molecular forces of attraction result in the particles becoming adsorbedon the substrate surface. The particle adsorption can be reinforced evenfurther by an overcoat at the same time, or in an additional procedure.

FIG. 3 shows a diagrammatic side view of a section of a device accordingto the invention for particle manipulation. Particle arrangements aresituated between the HF electrode 11 and the substrate 30, with theadjustment device 31 on the one hand and the grounded counter-electrode12 on the other. The particle arrangement 40 is designed with a multiplycurved cross-sectional shape, which essentially corresponds to theprogression of the static electrical field in the space between theelectrodes. The field between the electrodes is deformed via anelectrode structure 41 in a location-selective way. In the exampledepicted, the electrode structure is formed by additional electrodes 41(needle electrodes), which are exposed to a positive voltage, insulatedand passed through the counter-electrode 12. The particle arrangementfollows the location-selective deformation of the electrical field, sothat a multiply curved structure comes about. The additional electrodes41 can be arranged in rows or sheets. Instead of a positive potential,the additional electrodes 41 can also be exposed to a negativepotential.

Shown diagrammatically on the lower part of FIG. 3 are two examples of alocation-selective substrate coating with particle arrangementsmanipulated according to the invention. If the particle arrangement isformed in such a way that the cross-sectional shape exhibits curvesfacing the top, an approximation of the particle arrangements to thesubstrate 30 according to the aforementioned first or second alternativeresults in a coating pattern as reflected in the lower left part of FIG.3. By contrast, if a curve facing downward is set (through negativepotentials of the additional electrodes 41), the reciprocalapproximation results in an island-shaped coating according to the lowerright part of FIG. 3.

Any coating patterns, e.g., in the form of circles, rings, arcs, stripesor the like can be formed on the substrate surface via a suitableformation of the electrode structure or additional electrodes.Additional modifications are possible if the additional electrodes aremoveably arranged per FIG. 3, so that the manipulation of particles 40over time can be varied. Correspondingly, various coating patterns canbe applied to the substrate 30 in sequence.

An alternative configuration for the location-selective shaping of thefield between the electrodes is explained below drawing reference toFIGS. 4 to 7.

FIG. 4 shows an exploded view of a reaction vessel 20 being adapted foran implementation of the invention. The reaction vessel 20 is not onlyadapted for the adaptive electrode described below, but may also berealized in connection with the embodiments of the invention shown inthe other Figures. The reaction vessel 20 consists of an electrode seat201, which is embedded in the container bottom 202. The reaction spaceis enclosed by the container bottom 202 with electrode seat 201, thecontainer wall 203 and the container cover 204, and may be evacuatedusing the vacuum connection 205. The container cover 204 has an insertedwindow 206, which is mounted on a subunit 207 of the container cover204, which may be swivelled vacuum-tight with respect to the containercover 204. It may be provided for that the subunit 207 itself may beswivelled under vacuum. The window insert 206 is designed foraccommodating different monitoring or diagnosing means for the particlesmanipulated within the reaction chamber. The parts of the reactionvessel 20 are connected in the usual manner as for a vacuum vessel.Furthermore, through lateral flange units, additional differentdiagnostic units may be introduced.

FIG. 4 furthermore shows the adaptive HF electrode 11 and the groundedcounter electrode 12 (compare FIG. 1). The counter electrode 12 is ofring-shaped design to form a viewing opening for the monitoring means(not shown).

An enlarged top view of the adaptive electrode 11 is shown in FIG. 5.The adaptive electrode 11, according to the usual cylinder shape ofvacuum vessels for formation of a field shape undisturbed by externalcontainer installations, has an essentially circular edge 111. The edgecontains a ring electrode 112 and numerous electrode segments, which forthe example shown are compiled in electrode subunits 113. The ringelectrode 112 is shown as continuous electrode section made of anintegral piece and set up for field correction (flattening) of theelectrical field of the high segment electrode section. Alternatively,it is also possible to provide for a segmented electrode section insteadof the ring electrode 112, in which the segments are biased withidentical fields. In the transitional section between the electrodesubunits and the ring electrode, the subunits are modified in theirheight in such a manner that the ring (possibly milled out from below)may be pushed over the subunits.

The electrode subunits 113 are provided for in an internal section ofthe electrode 11, surrounded by the ring electrode 112, and each submitincluding numerous electrode segments. The shape, size and number ofelectrode segments is designed to be application-dependent underconsideration of the spatial requirements made of an electrical director low frequency field (E) between the electrodes 11, 12 (compare FIG.1). The largest variability of the adjustable field shape is achieved bya matrix arrangement of numerous point-shaped electrode segments(hereinafter referred to as “point segments” or “point electrodes”). Inthis respect, the designation point-shaped electrode segmentrespectively point segment means that each electrode segment has alimited area facing to the reaction chamber, but this has substantiallysmaller dimensions than the total size of electrode 11. For instance,each point electrode has a characteristic length dimension being smallerby a factor of about {fraction (1/500)} to {fraction (1/100)}, forinstance {fraction (1/300)} with respect to the outside dimensions(diameter) of the electrode 11. The matrix grid may be selected to belarger depending on the application. In case of the point grid shape ofthe adaptive electrode shown here, a characteristic length dimension ofthe point electrode is preferably equal to or smaller than the Debyelength of the particles within the plasma (for instance about 3 mm).

An adaptive electrode 11 for instance has an outside diameter of about50 cm at a width of the ring electrode 112 of about 5 cm, so that theinner section of the electrode segments 113 has a diameter of about 40cm. The adaptive electrode subunits 113 may in total for instanceinclude about 50,000 to about 100,000 point segments. A preferredmeasure for segmenting is a 1.27 mm grid compatible to available{fraction (1/20)} inch plug installations, as these are explained ingreater detail with reference to FIG. 6. In this case, about 80,000point segments electrically insulated from each other may be arrangedwithin the ring electrode 112.

For reasons of clarity, the lower part of FIG. 5 does not show everysingle point segment, but the electrode subunits (point segment groups).A groupwise combination of point segments is not a compellingcharacteristic of the invention, but has advantages in electrodecontrol, as this explained in detail below with reference to FIGS. 7 and8. For instance, the line pattern in the lower part of FIG. 5 by exampleshows the electrode subunits 113, which in each case contain 8·32 pointsegments. This is clarified by the upper part of FIG. 5, showing anenlargement of a section (X) of the edge of the electrode subunits 113.The invention is not limited to combining 8·32 point segments into oneelectrode subunit, but may, depending on construction and application,include other groupings (for instance 16·16 point segments).

The upper part of FIG. 5 by example shows highlighted an electrodesubunit 113 with a plurality of point segments or point electrodes 115,which in each case are electrically separated from each other by meansof insulation webs. The point electrodes 115 have square faces of thewidth a=1.25 mm pointed to the reaction chamber. The insulating stems116 have a width b=0.02 mm, so that in total the above mentioned 1.27 mmgrid results. The electrode subunit 113 for instance includes 8·32 pointelectrodes 115. It may furthermore be seen from FIG. 5 that the ringelectrode 112 and the section of the electrode subunits 113 reciprocallyoverlap. This achieves an optimum, dense filling of the internal sectorof electrode 11 even at the edge of ring electrode 112, as this can beseen in the enlarged part of FIG. 5.

The ring electrode 112 as well as the electrode subunits 113 consist ofa metallic electrode material. The material for the electrode isselected to be application-dependent and according to the desiredproduction procedure. In the case of the etching process describedbelow, for instance, stainless steel, aluminum or copper may be used aselectrode material. To avoid electrical interference by deposits on theelectrode surface, this is preferably coated with an insulating layer,which may for instance consist of the same insulating material as theinsulating webs 116. The insulating layer may for instance have athickness of about 10 μm to about 100 μm, preferably about 20 μm. Anymaterial is suited as insulation material for the insulation webs 116,which ensures sufficient insulation strength between the pointelectrodes for the voltages occurring. This insulation material is forinstance epoxy resin or another suitable plastic material.

FIG. 6 shows the composition of the segmented electrode by example of anelectrode subunit 113. According to the example explained above, theelectrode subunit 113 which includes 8·32 point electrodes 115. Theseform (together with the other segments not shown of the adaptiveelectrode) an upper electrode section which is also referred to assegmented electrode 120. The segmented electrode furthermore consists ofthe insulation plate 122, in which a plurality of sockets is embedded(not shown), whose quantity and arrangement in each case corresponds tothe point electrodes 115 of the electrode subunit 113. The sockets areprovided for accommodation of the plug units 123, which possibly mayalso take the form of an integrated base plate. It is also possible toinstall the plug units 123 as sockets and form an electrical connectionto the sockets integrated into the insulation plate to create conductivepins. There is an electrical connection between each socket of theinsulating plate 122 and the corresponding point electrode 115. Thecomposition of the insulating plate 122 depends on the productionprocess for the overall electrode 11 respectively for the section of theelectrode subunits 113. Such a production process is shown below byexample.

At first, from the lower side of the insulation plate 122, a drill holeis made for each point electrode 115 through the insulating plate 122 upto the later position of the respective point electrode 115, so that atthe end of each point-shaped electrode, which is fastened to theinsulating plate using conductive glue, an associated socket foraccommodating a pin of the plug-in device 123 is created. Then, ametallic plate or film made of the selected electrode material with thedesired outside diameter respectively thickness parameters is glued to aplate made of insulating material with a thickness corresponding to thedesired thickness of the insulating plate 122. Then material ablation isperformed from the metallic electrode film to form the point electrodes115, whereby the corresponding positions of the point electrodes aresituated above the holes in the insulating plate. For material ablation,channel-shaped free spaces according to the pattern of the insulatingwebs 116 (compare FIG. 5) are formed. This material ablation is byexample performed by a masked etching process, during which the metallicfilm is removed through to the insulating plate except in the desiredpositions of the point electrodes. Then, the channels for formation ofinsulating webs 116 are filled using an insulating material. This mayfor instance be performed by filling using hardening resin.

In the case of alternative procedures, using corresponding structuringprocedures, sockets are formed in the insulating plate 122, which ineach case in the direction of the adaptive electrode are closed andelectrically connected to the respective point electrode 115. In anycase, the segmented electrode forms a vacuum-tight end of the reactionchamber.

On the side of the plug units 123 looking away from the segmentedelectrode, boards 124 are mounted bearing the connecting plugs 126 toexternal electronics and addressing, decoder, multiplex and demultiplexcircuits 127, 128, 129, respectively, whose function is explained belowin detail with reference to FIG. 7. For the embodiment of the inventiondisplayed, four plug units 123 (including the boards 124) for in eachcase 2·32 point electrodes 115 are combined in one MUX module each forcontrol of 8·32 point electrodes. The distance of the four correspondingboards 124 is determined by the reference grid and is slightly largerthan the height of the superimposed circuits 127, 128, 129. Thisdimensioning may in turn be modified depending on size and application.The four boards 124 are connected to each other by partially conductivestabilizing units 126 a.

For easier handling (fitting of the segmented electrode with plugunits), it is possible to provide for color coding 117 on the lower sideof the insulating plate 122 for each electrode subunit 113. The boards124 are designed in such a manner that the electronic switchingcomponents shown in FIG. 7 may be integrated.

In the following, the electrical control of the adaptive electrode 11according to the invention is explained under reference to the blockdiagram according to FIG. 7. FIG. 7 shows, in the reaction vessel 20(see FIG. 4), point electrodes 115 as part of the HF electrode (adaptiveelectrode 11) and the counterelectrode 12 (also see for instance FIG.1). Of the (in total 256) point electrodes 115 of an electrode subunit113, the first and last point electrode of the first and fourth board124 are in each case shown enlarged (matrix positions (1,1), (2,64),(7,1), (8,64). Furthermore, the ring electrode 112 is shown.

The electronics section 130 includes all boards 124 (see FIG. 6)allocated to the point electrodes 115. For example, a board 124 for 8·32point electrodes 115 is shown. The electronics section 130, being thereverse side of the adaptive electrode 11 looking away from the reactionchamber, is subject to a vacuum to avoid excess pressure load on theadaptive electrode 11. The pressure in the electronics section 130 mayfor instance be in the range from about 10 to about 100 mbar.Alternatively, the electronics section may, as pressure relief for theadaptive electrode, also be filled using an insulating liquid, such asfor instance oil, which also may assume a cooling function. Separatedfrom the electronics section 130 are under atmospheric conditions supplycircuits 140 and a control device 150 provided for. The supply circuits140 include an HF generator 141, a power supply circuit 142 for the ringelectrode 12 and a control voltage circuit 143.

The board 124 has a coupling circuit 131 for each of the pointelectrodes 115. The coupling circuit 131 is provided for biasing eachpoint electrode (respectively generally each electrode segment) of theadaptive electrode 11 simultaneously with the output voltage of the HFgenerator 141 and with segment-specific output voltage of the controlvoltage circuit 143. According to the invention, the fact is exploitedwith special advantage that the HF supply is a high frequency signal andthe location-selective creation of field distribution in the reactionchamber is with low frequency signal respectively using a staticelectrical field. For instance, the output parameters of the HFgenerator 141 have an output frequency in the MHz range (correspondingto the usual frequencies for creation and maintaining plasma, forinstance 12 to 15 MHz), and a voltage range of ±150 V_(SS) (sineshaped). In contrary to this, bias for the point electrodes 115 isperformed by low frequency (≦100 Hz) or static (direct voltage, DC)control voltages. Accordingly, each coupling circuit 131 contains acapacitor-resistor combination (C1-C256, R1-R256), whereby the HFperformance is coupled in jointly through all capacitors.

Each board furthermore provides for an addressing circuit 132, whichincludes the above mentioned (see FIG. 6) address decoder, multiplexerand demultiplexer circuits 127, 128, 129, which cooperate as follows.

The address decoding circuit 127 depending on the switching signals(DEMUX CONTROL and MUX CONTROL) of the control circuit 150 selects whichvoltage is switched by the control voltage circuit 143 includingmultiplex circuit 128 to a central line 133 using a switching frequencyof 256 kHz, and from this using the demultiplex circuit 129 to acoupling circuit 131, again selected by the address decoding circuit127, according to a point electrode 115. For the embodiment shown, thecontrol voltage circuit 143 supplies 64 control voltages to 64 supplylines (also compare FIG. 7). The control voltages on the power supplybus 143 a for instance differentiate by voltage steps of 0.625 V andcover the range of ±20 V (direct voltage). Accordingly, the multiplexcircuit 128 makes a 1:64 selection for connection of one of the 64supply lines 143 a with the central line 133. For the embodiment shown,furthermore 256 coupling circuits 131 according to the 256 pointelectrodes 115 are provided for, so that the demultiplex circuit 129makes a 256:1 selection from the central line 133 to one of the couplingcircuits 131.

The point electrodes 115 belonging to a board 124 (according to anelectrode subunit) are preferably controlled serially according to acertain sequential pattern. In this respect, with special advantage, adual function of the coupling capacitors C1-C256 is used. These do notonly serve coupling of the HF signal, but also maintenance of theelectrode potential at the individual point electrodes for as long as,according to the serial control sequence, there is no connection to thecontrol voltage circuit 143. Because from each point electrode 115 thereis a constant current leakage through the plasma, the couplingcapacitors C1-C256 must be cyclically recharged to the desired voltage.The coupling capacitors are designed so that the discharge at therespectively coupling capacitor for application-dependent electrodevoltages respectively power loss and therefore the voltage loss at theassociated point diode during a control cycle is (≦1%) with respect tothe electrode voltage.

The switching frequency of the address decoding circuit 127 is selecteddepending on the number of point electrodes 115 belonging to a subunit113, on the frequency of the control voltage changes and on the voltageconstancy during a cycle at the point electrodes, so that the serialcycle sequence by the subunit or segment group 113 has a substantiallyhigher frequency than the low frequency voltage of the control voltagechange. This for instance means in case of 256 point electrodes and adesired cycle frequency of about 1 kHz (corresponding to 1,000recharging processes for each point electrodes per second) a switchingfrequency of 256 kHz. This fast switching between the voltage stages ofthe control voltage circuit 143 also enables location-selective modelingof the field shape in the reaction chamber 20 according to pulsatingfield behavior.

The overall control electronics 140, 150 according to FIG. 7 issuperimposed on the HF signal with respect to potential and, therefore,decoupled from the control computer, the network and other interfacesfor cooling purposes, etc. with low capacitance. Input of controlsignals using a control device 150 is preferably performed using anoptical coupler.

The adaptive electrode 11 described above and the associated controlelectronics may be modified as follows. The number, shape andarrangement of electrode segments may be modified depending on theapplication. When realizing a matrix using point electrodes, thecompilation in segment groups may be modified depending on applications.The same holds true for the voltage range of the control voltage circuit143 and the size of the adjustable voltage steps or stages. Finally, thedevice in the reaction vessel (see FIG. 4) may be reversed by fittingthe grounded electrode 12 on the lower and the HF electrode 11(especially the adaptive electrode 11) on the upper side.

An important advantage of the adaptive electrode 11 is creation of aprogrammable spatial stationary or low-frequency electrical field shapewithin the reaction chamber, by which charged particles may be held incertain locations or moved in a certain manner. This allows theparticles to be manipulated so that they can be positioned in anymanner.

FIG. 9 shows a diagrammatic side view of parts of a device according tothe invention, in which the plasma particle arrangement 50 takes theform of steps between the HF electrode 11 and the substrate 30, with theadjustment 31 on the one hand and the counter-electrode 12 on the other.This shape can be achieved, for example, by using a discharging orcharge reversing device according to FIG. 2. Partially irradiating theparticles with UV light discharges a portion of the particles (left areain FIG. 8), so that the equilibrium is set at a slight height over theHF electrode 11 given unchanged plasma conditions. Correspondinglychanging the relative position of the particle arrangement 50 and/orsubstrate 30 makes it possible to achieve a partial coating of thesubstrate 30, as illustrated in the lower part of FIG. 8.

The HF electrode 11 can be structured with structural elements 61according to FIG. 8 to influence the electrical field between the HFelectrode 11 and counter-electrode 12 in such a way that the particlearrangement becomes situated only in an area with a potential minimumlocated over the particles of the HF electrode 11 that are not coveredby the structural elements 61. For example, if the structural elements61 are formed by cover beams that leave a striated gap, the particlearrangement 60 is striated (extends perpendicular to the drawing planeof FIG. 9). The particle arrangement 60 can in turn be deposited on thesubstrate 30 according to the invention.

As an alternative to the striated design, according to FIG. 9, a portionof the HF electrode 11 can be structured or masked with structuralelements 61.

FIG. 10 shows another possibility for exercising outside adjustmentforces on the particle arrangement. The diagrammatic top view of adevice according to the invention shows the HF electrode 11 with thecontrol device 13 and the substrate 30 with the adjustment device 31.The HF electrode 11 carries structural elements (not shown) according toFIG. 10, so that a striated particle arrangement comes about. The shapeof the particle arrangement 70 can be further altered by exposingdeflecting electrodes 71 synchronously with an alternating voltage(control circuit 72). The deflecting electrodes 71 are set up for alateral deflection of a striated particle arrangement in the layerplane. This makes it possible to achieve a serpentine oscillation ofparticles of the kind shown in FIG. 10, for example. This arrangementcan in turn be applied to the substrate 30.

FIG. 11 shows a surface coating with longitudinally stretched particles,which is set up in particular for achieving anisotropic optical surfaceproperties. The longitudinally stretched particles 80 can be so-called“Bucky Tubes” (microscopic, tubular particles consisting of a uniformarrangement of carbon atoms). The Bucky Tubes can exhibit a length ofseveral micrometers and a diameter of roughly 10 to 20 nm, for example.These particles have a relatively large surface, which leads to a strongcharge in the plasma and to polarization. A discharge induced byenergetic irradiation triggers a corresponding approach to the substrate30 and adsorption of the longitudinally stretched particles with apreferred vertical direction, as illustrated in the lower part of FIG.11. If necessary, these adsorbates can be fixed in position by anadditional coating in an extra step.

According to FIG. 12, which shows a top view on parts of a deviceaccording to the invention, the particle arrangement 90 can bemanipulated by exerting a radiation pressure from an outside lightsource 91. The outside control light source can be comprised of ahelium-neon laser with a power of roughly 10 mW, for example. Theradiation pressure exerted on the particles with the laser beam makes itpossible to precisely check the position, which can be monitored with amonitoring device 17 (see FIG. 1). The radiation pressure can be usedfor the preferred rotation of particle arrangements (see arrow), or tomove them onto a laterally situated substrate.

In addition to the illustrated embodiments of the invention, additionalmodifications of the device according to the invention are conceivableby setting up means with which the conditions of the particlearrangements can be altered in a location-selective manner by exertingoutside forces. For example, it is possible to use a magnetic fielddevice for the targeted control of the plasma, e.g., via a magneticfield directed perpendicular to the electrode planes. In addition, it ispossible to dynamically execute the coating process, wherein particlesare continuously fed to the plasma space and applied to the substratesurface in a location-selective manner. Additional modifications relateto the substrate. The substrate need not be flat, but instead canexhibit bent surfaces. Several substrates can be present.

It is also possible to operate a device according to the invention as adisplay device without application to a substrate, wherein anisotropicparticles can be switched between various orientations to indicatepredetermined patterns, e.g., each representing a “blackening” or“transparence” state. It is also possible to manipulate particles ofvarious size in different heights of a plasma and illuminate them fromthe side with excitation light sources of varying wavelengths, so thathigh-resolution, color displays can be built up.

One special advantage to the invention is that it can be implemented byinexpensively modifying conventional plasma reactors (e.g., from circuitproduction), whose operating conditions are well-known and controllable.The invention can be used to fabricate so-called designer materials withspecial surface properties.

Second Embodiment

The second embodiment differs from the first embodiment described aboveonly in that the particles are not externally supplied to the reactionspace via a dispenser or the like, but rather come about in thisreaction space as the result of aggregation processes in the reactiongas. This includes the aforementioned particle formation insilane-containing reaction gases during the CVD deposition of amorphoussilicon layers. However, corresponding applications are possible in allother CVD deposition procedures, in particular with respect tosemiconductors.

According to the invention, particles that arise during the plasmadeposition in the reaction gas are manipulated with the same meansdescribed in relation to the first embodiment above. In particular, itis provided that the particles be discharged or undergo a chargereversal in predetermined partial areas of their formation as the resultof a location-selective, energy-rich irradiation. The partial areascorrespond to specific deposition patterns according to which theparticles are to be embedded into the layer growing on a substrate inthe reaction vessel. The deposition patterns are selected to achieve thedesired optical or photoelectric properties of the separated layer.Characteristic dimensions of the deposition patterns extend from theresolution limit of the respectively selected energy-rich irradiation(nm range) up to the dimensions of the plasma electrodes.Location-selective deposition is performed simultaneously to layerdeposition due to the fact that the particles can be disrupted by thedischarge or charge reversal in the equilibrium of force of the fieldsin the reaction space, and hence can sink down onto the substrate. If noadditional, static electrical field is provided as described above tobring about the equilibrium of forces, the discharge or charge reversalprocess on the particles allows them to traverse the space charge regionin proximity to the electrodes or substrate, which would shield thenegatively charged particles.

Therefore, the invention also relates to an amorphous semiconductorcoating with embedded particles, wherein the particles are limited tospecific partial areas of the layer based on a predetermined depositionpattern. The deposition patterns encompass both the lateral particledistribution in the layer plane, as well as a particle distributionsubstantially perpendicular to the layer plane given a time dependentchange in the location-selective discharge or charge reversal processeson the particles in the reaction gas. Therefore, any spatialdistributions of particles can be achieved in layers generated viaplasma deposition.

In the second embodiment, it is also possible in particular to processthe particles in the reaction gas prior to deposition, as was describedabove drawing reference to the first embodiment. Through exposure toelectrical control fields and energetic irradiation, the particles canbe transferred for discharge or charge reversal purposes into a plasmaarea where the particle surface is stripped or the particles are coatedwith an additional material, wherein the deposition in the layer on thesubstrate takes place after this processing step.

What is claimed is:
 1. A process for manipulating particles in a plasmaof a carrier gas or reaction gas within a reactor vessel having highfrequency electrodes and a substrate arranged between said electrodescomprising: distributing the particles substantially non-unifonnly as anon-uniform spatial particle distribution in the plasma, wherein Coulombinteraction between the particles is so low that the particlessubstantially do not form a plasma crystalline state, the particledistribution being held in a balance between gravitational andelectrical forces and the substrate being arranged between the particledistribution and one of the electrodes, modifying the shape of theparticle distribution by location-selective effecting the balancebetween gravitational forces and electrical forces, and arranging andadhering at least a portion of the particles from the modified particledistribution on the substrate by one or more selected from influencingthe electrical forces, exerting external adjustment forces holding theparticles, moving the substrate and modifyiing plasma conditions in thevessel.
 2. A process for manipulating particles in a plasma of a carriergas or reaction gas within a reactor vessel having high frequencyelectrodes comprising: distributing the particles substantiallynon-uniformly as a non-uniform spatial particle distribution in theplasma, wherein Coulomb interaction between the particles is so low thatthe particles substantially do not form a plasma crystalline state, theparticle distribution being held in a balance between gravitational andelectrical forces, moving a predetermined portion of the particledistribution to a treatment position by location-selective effecting thebalance between gravitational forces and electrical forces, by exertingexternal adjustment forces or by modifying the plasma conditions, andsubjecting the particles in the treatment position to a plasma treatmentcomprising a particle surface coating or ablation.
 3. The processaccording to claim 1 or 2, wherein the external adjustment forces areselected and are generated in a location-selective manner via anelectrical particle discharge, a particle charge reversal or a lightradiation pressure.
 4. The process according to claim 3, wherein theelectrical particle discharge or the particle charge reversal areselected and takes place via location-selective UV, electron irradiationor laser charge reversal of the particles.
 5. The process according toclaim 1 or 2, wherein modifying the plasma conditions is used and thechange in the plasma conditions encompasses a change in plasma pressure,plasma temperature, the carrier gas, plasma energy and/or an operatingfrequency of the plasma, deactivation of plasma generation or aninfluencing of electrical fields in an area of the particles.
 6. Theprocess according to claim 5, wherein the influencing of electricalfields is selected and encompasses setting a static or low-frequencyvariable electrical field in such a way that the particles becomearranged or move at a low frequency along a predetermined, bent surfaceor in an area with predetermined.
 7. The process according to claim 1,wherein the particles are elongated and rod-shaped and applied to thesubstrate surface in such a way that the rod shape essentially extendsperpendicularly from the substrate surface.
 8. The process according toclaim 1 or 2, wherein the particles are formed in the reaction gas orintroduced into the plasma outside the reactor vessel.
 9. The processaccording to claim 1, wherein, while coating takes place with a plasmachemical vapor deposition (CVD) deposition process on the substrate froma reaction gas, particles formed in the reaction gas are manipulated orsimultaneously embedded in the coating.
 10. The process according toclaim 9, wherein the particles are nanocrystalline semiconductorparticles which are embedded in the coating which is a semiconductorlayer according to a predetermined deposition pattern.
 11. The processaccording to claim 10, wherein the semiconductor layer with the embeddednanocrystalline semiconductor particles is part of a photovoltaicdevice.
 12. The process according to claim 1 or 2, wherein the particleshave characteristic sizes of a few nanometres to 10 nm.